In practical application, diesel motors are used as the main engines in road pavers. Both the diesel motors and the assemblies driven by them have, due to their degree of efficiency, thermal power loss that must be dissipated by a cooler in order to prevent the driven assemblies from overheating.
It is known that in current pavers, three working media, namely cooling water, charge air and hydraulic oil, are cooled to the required temperatures by means of heat exchangers. In order to ensure airflow through the heat exchangers, a fan is a component of the cooling system.
In the case of conventional road pavers, the fan is connected rigidly to the diesel motor so that the fan takes on an operating rotational speed equal to the diesel motor rotational speed at all times. This is detrimental because even in the case of a short-term rise in the diesel motor rotational speed, the fan likewise runs at a higher speed, as a result of which considerable noise can develop. Such synchronous operating performance of the ventilator is, however, not needed in practice, because the fan operation depends more on the required temperatures of the working media than on a need to be driven synchronously with the diesel motor rotational speed.
As an alternative to a rigid coupling of the fan to the diesel motor, in practice hydraulically driven fans are used on road pavers. This has the disadvantage, however, that hydraulic losses must be accepted in the fan drive. In addition, the financial expenditure increases enormously if one wants to optimise the degree of efficiency of a hydraulic fan drive.